(a) Technical Field of the Invention
The present invention relates to a safety for nailing devices, and in particular to a safety that, unless released, prevents a nail striker plate from being moved to a ready-to-strike position in order to prevent the nailing device from being accidentally triggered to undesirably shoot nails.
(b) Description of the Prior Art
In modern carpentry, a nailing device has been commonly used to function as an automatic nailing too that repeatedly feed out nails. A regular nailing device comprises a housing having a lower portion in which a nail channel is defined for accommodating a strip of nail. A nail feeding device is also provided in association with the nail channel to advance the nail strip. A nail striker plate is arranged inside a housing and movable up and down. When the striker plate is moved upward to a ready-to-strike position, the nails that make up the nail strip are sequentially advanced to a struck position where the nail is forcibly struck out of the housing and into a work piece when the striker plate is triggered.
The conventional nailing device is operated by lifting the striker plate to set the striker plate in a ready-to-strike condition and instantaneously releasing the striker plate to complete the nailing operation. Thus, when the nailing device is not in operation, if the striker plate is undesirably moved to the ready-to-strike position by an accidental actuation of for example an operation handle, then nail may be mistakenly shot and since it is possible that the nailing device is not properly set on a work piece at this time, the mistakenly shot nail may cause damage to operators or other persons staying around or properties. Thus, a safety is often provided. An example is a safety ring that secures, in a releasable manner, the operation handle to the housing to prevent the handle from driving the striker plate to the ready-to-strike position. However, in use of the nailing device, the safety ring must be released to allow the nailing device to be set in a ready-to-strike condition, and therefore inadvertent percussion at the time that the nailing device is not properly set on a work piece may happen, which may hurt the operator or other persons standing nearby by shooting uncontrolled nail.
To cope with such a problem, Taiwan Patent No. I281432 discloses a nailing device comprising a housing in which a safety bar is movably arranged in such a way that the safety bar is normally projecting out of a bottom of the housing. The safety bar functions to prevent an engaging portion formed on a handle from engaging an opening defined in a striker plate. When the nailing device is properly set on a work piece, the safety bar is forced into the housing, allowing the handle to engage the striker plate for setting the nailing device in a ready-to-strike condition. As such, inadvertent percussion of the nailing device can be avoided.
The known device uses a biasing torque provided by a torsion spring to disengage the engaging portion of the handle from the opening of the striker plate in order to realize prevention of inadvertent percussion. However, when the operator of the nailing device applies a force that exceeds the spring force, the engaging portion of the handle may also get back into engagement with the opening of the striker plate to cause undesired percussion. Apparently, the known device is not capable to fully eliminate the potential risk of inadvertent percussion.
In view of the above discussed issue, the present inventor has engaged in researches in the related fields, attempting to ensure an improvement that secures the operation safety of a nailing device by incorporating a novel safety to eventually and completely overcome the problem associated with inadvertent percussion of the conventional nailing devices.